Transfer case sprocket idler gear actuation

ABSTRACT

A transfer case includes first and second output shafts selectively driven by an input shaft. A first gearset is driven by the input shaft providing first and second gear ratios to the first output shaft. A range actuator includes an axially moveable member operable to shift the first gearset between the first and second gear ratios. An actuation shaft is coupled to the axially moveable member such that rotation of the actuation shaft translates the axially moveable member. A second gearset is driven by the input shaft and drives the actuation shaft. The second gearset includes a control gear moveable into and out of meshed engagement with a first gear and an idler gear. The actuation shaft is rotated in a first direction when the control gear is meshed with the first gear and rotated in an opposite direction when meshed with the idler gear.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. National Phase of International Application PCT No. PCT/US2012/024070 filed Feb. 7, 2012. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to a shift system for a power transmission device for a vehicle. The shift system utilizes the kinetic energy of a moving driveline component to accomplish a shift.

BACKGROUND

In general, power transfer mechanisms, such as transfer cases, may be operatively associated with either manual or automatic transmissions for selectively directing power from an engine to a first set of driven wheels in a two-wheel drive mode, as well as selectively directing power to a second set of wheels for operation in a four-wheel drive mode. Many transfer cases provide for a mode shift when transferring between two-wheel and four-wheel drive modes, as well as a range shift to provide at least two different reduction ratios to the driven wheels.

Some transfer cases include a range shift system axially translating a range sleeve between low range, neutral and high range positions. The range shift system may include a range shift fork for the application of force to the range sleeve. To achieve a range shift, an actuator typically including a relatively large electric motor, applies a force to the range shift fork. Other mechanical torque transferring devices may be positioned between electric motor and the range shift fork to multiply the apply force provided to the range shift fork. For example, some range shift systems include ball ramp actuators, pilot clutches, and the like.

In some arrangements, the magnitude of force required at the range shift fork to complete a range shift may be significant. Accordingly, the size of the electric motor and the quantity of energy required to complete a shift may be greater than desired. As such, it may be desirable to provide a range shift system operable to use the energy from a driveline component to complete a range shift.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A transfer case includes first and second output shafts selectively driven by an input shaft. A first gearset is driven by the input shaft providing first and second gear ratios to the first output shaft. A range actuator includes an axially moveable member operable to shift the first gearset between the first and second gear ratios. An actuation shaft is coupled to the axially moveable member such that rotation of the actuation shaft translates the axially moveable member. A second gearset is driven by the input shaft and drives the actuation shaft. The second gearset includes a control gear moveable into and out of meshed engagement with a first gear and an idler gear. The actuation shaft is rotated in a first direction when the control gear is meshed with the first gear and rotated in an opposite direction when meshed with the idler gear.

A transfer case includes an input shaft as well as first and second output shafts. A planetary gearset including a sun gear, a ring gear, a carrier and a pinion gear rotatably supported by the carrier. The pinion gear is meshed with the sun and ring gears. A range actuator includes first and second range sleeves that are axially translatable between a first position to provide a drive connection between the input shaft and the first output shaft. At a second position, a direct drive ratio connection between the input shaft and the first output shaft as well as the input shaft and the second output shaft is provided. At a third position, a reduced speed drive ratio connection between the input shaft and the first output shaft as well as the input shaft and the second output shaft is provided via the planetary gearset. The range actuator includes an actuation shaft drivingly coupled to the first range sleeve such that rotation of the actuation shaft translates the first range sleeve. Another gearset is driven by the input shaft and drives the actuation shaft. The another gearset includes a first gear, an idler gear and a control gear. The control gear is moveable into and out of meshed engagement with the first gear and the idler gear. The actuation shaft is rotated in a first direction when the control gear is meshed with the first gear and rotated in an opposite direction when meshed with the idler gear.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a cross-sectional view of an exemplary transfer case equipped with a range actuator constructed in accordance with the teachings of the present disclosure;

FIG. 2 is a fragmentary perspective view of a portion of the transfer case and the range actuator;

FIG. 3 is another perspective view of a portion of the transfer case and the range actuator;

FIG. 4 is a fragmentary cross-sectional view taken through the transfer case of FIGS. 1-3 having the components of the range actuator depicted in their proper 3-D position;

FIG. 5 is a fragmentary enlarged sectional view of a portion of FIG. 1;

FIG. 6 is a fragmentary cross-sectional view of another transfer case equipped with another range actuator;

FIG. 7 is a fragmentary perspective view of the transfer case and range actuator depicted in FIG. 6; and

FIG. 8 is another fragmentary perspective view of the transfer case and range actuator depicted in FIG. 6.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

With reference to the Figures, a transfer case constructed in accordance with the teachings of the present disclosure is identified at reference numeral 10. Transfer case 10 is operable to transfer torque from the input shaft 12 to one or both of a first output shaft 14 and a second output shaft 16. First output shaft 14 is drivingly coupled to a first set of driven wheels. Second output shaft 16 is drivingly coupled to the second set of driven wheels.

Transfer case 10 is operable to transmit torque from input shaft 12 to the vehicle wheels via sets of sliding splines as will be described. Depending on the position and engagement of the splines, power may be transferred from input shaft 12 to only first output shaft 14 in a two wheel high/four wheel drive automatic mode via the use of an active clutch 17, a four wheel drive high Lock mode and a four wheel drive Low mode of operation. A neutral position is also provided. The components of transfer case 10 are arranged such that input shaft 12 may be disconnected from components of a planetary gearset 18 such that the planetary is stationary until torque is required to be transferred through planetary gearset 18. Vehicle efficiency is not a primary goal when transfer case 10 operates in the low range. As such, the additional drag associated with rotating the components of planetary gearset 18 in this mode is acceptable.

Transfer case 10 includes a range actuator 20 operable to selectively translate a first range sleeve 22, a second range sleeve 24 and a third range sleeve 26 to a number of different axial positions to provide the drive modes previously described.

First range sleeve 22 includes a spline 32 engaged with a spline 34 formed on first output shaft 14. A set of clutch teeth 36 are also formed on first range sleeve 22. Second range sleeve 24 abuts first range sleeve 22 and includes a spline 38 drivingly engaged with spline 34 of first output shaft 14 and a spline 40 formed on input shaft 12. Clutch teeth 42 are formed on second range sleeve 24. Third range sleeve 26 abuts second range sleeve 24 and includes a spline 48 drivingly engaged with a spline 50 of a drive sprocket 52.

Drive sprocket 52 forms a portion of a transfer mechanism 54 operable to transfer torque to second output shaft 16. More particularly, a flexible member such as a chain 58 drivingly engages drive sprocket 52 as well as a driven sprocket 60. Driven sprocket 60 is fixed for rotation with second output shaft 16. Clutch teeth 62 and 64 are formed at spaced apart locations on third range sleeve 26.

Planetary gearset 18 includes a ring gear 70 fixed to a housing 72 of transfer case 10. A sun gear 74 is provided with clutch teeth 76. A plurality of pinion gears 78 are drivingly engaged with ring gear 70 and sun gear 74. A plurality of pins 80 support pinion gears 78 for rotation thereon. A first carrier plate 84 is rotatably supported by a bearing 86 and includes a plurality of clutch teeth 88. First carrier plate 84 supports pins 80. A second carrier plate 90 also supports pins 80 and includes clutch teeth 94.

FIG. 1 represents transfer case 10 being operated in a two-wheel high drive mode of operation. At this time, torque is transferred from input shaft 12 to second range sleeve 24. Second range sleeve 24 is drivingly engaged with first output shaft 14 to drive the first set of vehicle wheels. The various clutch teeth previously described are disengaged from the components of planetary gearset 18. Operation and efficiency of transfer case 10 is high due to the fact that planetary gearset 18 is not being driven and transfer mechanism 54 is not being driven in the two wheel high drive mode.

To provide a four wheel drive high lock mode of operation, range actuator 20 axially translates first range sleeve 22 to the position identified as HL. At this time, each of first, second and third range sleeves 22, 24 and 26 are translated to new positions. In particular, third range sleeve 26 is drivingly engaged with input shaft 12 via a set of gear teeth 100 as well as drive sprocket 52. Second range sleeve 24 remains simultaneously engaged with input shaft 12 and first output shaft 14. As such, a four wheel drive high locked mode of operation is provided. It should also be appreciated that during this mode of operation, none of the components of planetary gearset 18 are driven.

In a neutral mode of operation, each of first, second and third sleeves 22, 24 and 26 are further axially translated to the positions identified as N. In the neutral mode of operation, teeth 62 and 64 of third range sleeve 26 are disengaged from the other components. Similarly, spline 38 of second range sleeve 24 is disengaged from first output shaft 14. No torque is transferred from input shaft 12 to either first output shaft 14 or second output shaft 16 in the neutral mode of operation.

To achieve the four wheel low drive mode, range actuator 20 further axially translates each of the range sleeves to the L position. In the four wheel low mode of operation, second range sleeve 24 drivingly connects input shaft 12 with sun gear 74 through the driving interconnection of teeth 42 and teeth 76. Speed is reduced and torque is multiplied through planetary gearset 18 where first carrier plate 84 and second carrier plate 90 act as output members. Torque is transferred from second carrier plate 90 to first range sleeve 22 via meshed engagement of teeth 94 and teeth 36. Similarly, first carrier plate 84 transfers torque to third range sleeve 26 via clutch teeth interconnection 64 and 88. Third range sleeve 26 remains drivingly coupled to drive sprocket 52 to transfer torque to second output shaft 16.

A coupling 102 interconnects first range sleeve 22 and second range sleeve 24. Coupling 102 includes a first thrust washer 104 positioned between first range sleeve 22 and second range sleeve 24. A second thrust washer 106 is positioned between second range sleeve 24 and a snap ring 108. Snap ring 108 is fixed to first range sleeve 22. Coupling 102 couples first range sleeve 22 and second range sleeve 24 for concurrent axial translation with one another. Coupling 102 allows relative rotation between first range sleeve 22 and second range sleeve 24. Coordinated movement of first range sleeve 22 and second range sleeve 24 is assured in both axial directions.

Second range sleeve 24 is coupled to third range sleeve 26 by a connector 122. Connector 122 may include a metallic sleeve having a cylindrically shaped center portion 124 overlapping an end 126 of second range sleeve 24 and an end 128 of third range sleeve 26. Second range sleeve 24 includes a groove 132 in receipt of a first downturned portion 134 of connector 122. A running clearance exists between cylindrical portion 124, first downturned portion 134 and second range sleeve 24. A groove 136 is formed on third range sleeve 26. Connector 122 includes a second downturned portion 138 positioned within groove 136. Second downturned portion 138 and substantially cylindrical portion 124 are clear of third range sleeve 26 such that second range sleeve 24 is axially coupled to third range sleeve 26 but relative rotation between the second and third range sleeves may occur. It is contemplated that connector 122 is constructed from a malleable metal initially shaped as a cylinder. A crimping operation may be used to define first downturned portion 134 and second downturned portion 138. A low cost, low weight coupling is provided.

Range actuator 20 is operable to selectively translate first range sleeve 22, second range sleeve 24 and third range sleeve to the various axial positions previously described. Range actuator 20 includes a shift fork 150 that is driven to an axial position corresponding to the transfer case modes previously described. An actuation shaft 152 is supported for rotation within housing 72 by bearings 154, 156. Actuation shaft 152 passes through and is drivingly engaged with a carrier 160. A thread 161 is formed on actuation shaft 152. Rotation of actuation shaft 152 axially translates carrier 160. A sleeve 162 surrounds a portion of carrier 160 and is axially moveable relative thereto. Sleeve 162 cooperates with a spring 164 and shift fork 150 to center sleeve 162 and shift fork 150 relative to carrier 160. The spring and sleeve arrangement allows carrier 160 to temporarily translate while shift fork 150 remains stationary during a blocked shift. Spring 164 continues to load shift fork 150 and first range sleeve 22 toward a desired axial position during the blocked condition. Once the blocked shift has cleared, shift fork 150 completes its targeted motion.

A gear train 170 is provided to transfer torque from drive sprocket 52 to actuation shaft 152 during a range shift. An operator 174 cooperates with gear train 170 to rotate actuation shaft 152 in one of a first direction or an opposite second direction. Gear train 170 includes a drive gear 178 fixed for rotation with drive sprocket 52. A driven gear 180 is in constant mesh engagement with drive gear 178. An intermediate shaft 182 is supported within housing 72 by bearings 184, 186. Intermediate shaft 182 passes through an aperture 188 formed in shift fork 150. Driven gear 180 is fixed for rotation with intermediate shaft 182. An axially translatable control gear 190 is splined for rotation with intermediate shaft 182. Control gear 190 is shown at a disengaged or neutral position in FIG. 1. An output gear 194 is fixed for rotation with actuation shaft 152. Control gear 190 may be axially translated to the left as viewed in FIG. 1 to meshingly engage drive output gear 194.

An idler shaft 196 is supported for rotation within housing 72 by a first bearing 198 and a second bearing 200. A first idler gear 204 is fixed for rotation with idler shaft 196. A second idler gear 206 is axially spaced apart from first idler gear 204 and also fixed for rotation with idler shaft 196. Second idler gear 206 is positioned in constant mesh engagement with output gear 194. Control gear 190 may be axially translated to the right as viewed in FIG. 1 to meshingly engage first idler gear 204. It should be appreciated that FIG. 1 depicts each of the components of gear train 170 lying along the plane of the figure for ease of description. The perspective views of FIGS. 2 and 3 as well as the cross-sectional view of FIG. 4 more accurately depict the three dimensional positioning of the components.

Operator 174 includes an electric motor 210 having a threaded output shaft 212. A control fork 214 is in threaded engagement with output shaft 212 such that rotation of output shaft 212 causes axial translation of control fork 214. A groove 216 formed in control gear 190 is in receipt of control fork 214. Electric motor 210 is sized to only provide enough energy to axially translate control gear 190 to the positions described. The energy to axially translate first range sleeve 22, second range sleeve 24 and third range sleeve 26 is provided from drive sprocket 52.

A shift fork position sensor 218 cooperates with shift fork 150 to output a signal indicative of the axial position of first range sleeve 22. A plurality of detents 220 are formed in shift fork 150. Shift fork position sensor 218 may include the plunger operable to enter and exit detents 220 as shift fork 150 translates. A speed sensor 224 is operable to output a signal indicative of the rotational speed of output gear 194. A controller 228 is in communication with electric motor 210, shift fork position sensor 218 and speed sensor 224 to properly position and confirm the position of shift fork 150. For example, controller 228 may determine the rotational speed and direction of rotation of output gear 194 based on the signal provided by speed sensor 224. Controller 228 uses the geometry of the threaded interconnection between actuation shaft 152 and carrier 160 in combination with the speed and direction of rotation of actuation shaft 152 to determine the direction and magnitude of linear travel of carrier 160. Controller 228 is also in communication with an actuator 232 operable to vary the input force provided to active clutch 17.

In operation, electric motor 210 may be actuated to rotate output shaft 212 in a direction to translate control fork 214 in a direction that urges control gear 190 to move toward the left as viewed in FIG. 1. Control gear 190 meshes without output gear 194. Clutch 17 may be controlled to transfer torque from input shaft 12 to drive gear 178. Controller 228 also energizes actuator 232 to transfer torque across active clutch 17. Torque is transferred from drive gear 178 to actuation shaft 152 to translate shift fork 150 in a first direction such as the direction moving first range sleeve 22 from position H to position HL. Once shift fork position sensor 218 indicates that the HL position has been reached, electric motor 210 is energized to rotate output shaft 212 in an opposite direction to axially translate control gear 190 out of engagement with output gear 194. Similar shifts may occur when a right to left movement of shift fork 150 is desired.

To translate shift fork 150 in the opposite direction or from left to right as viewed in FIG. 1, electric motor 210 is energized to rotate output shaft 212 in a direction to cause control fork 214 to move control gear 190 to the right. Control gear 190 drivingly engages first idler gear 204 and electric motor 210 is no longer energized. Torque may once again be transferred across clutch 17 to rotate drive gear 178 and the other members of gear train 170. Because control gear 190 is now meshingly engaged with first idler gear 204, torque is transferred through idler shaft 196 and second idler gear 206 to output gear 194. Output gear 194 is rotated in the opposite direction as previously described. Actuation shaft 152 is rotated in a direction to cause shift fork 150 to move from the left to the right as viewed in FIG. 1. It should be appreciated that actuator 20 exhibits improved controllability as compared to previously known designs as the engagement speed of the first, second and third sleeves 22, 24, 26 may be adjusted based on controlling active clutch 17. In addition, through the use of multiple spur gears in gear train 170 and a relatively small electric motor 210, the electrical energy and packaging space required to accomplish a range shift are minimized.

FIGS. 6-8 depict an alternate range actuator 300. Range actuator 300 is substantially similar to range actuator 20 with the exception that a drive gear is no longer fixed for rotation with the drive sprocket but alternatively placed in driving engagement with chain 58. More particularly, a drive gear 302 is fixed for rotation with an intermediate shaft 304 that is supported for rotation in a housing 305 by bearings 306, 308. A snubber or guide plate 310 is positioned on an opposite side of chain 58 as drive gear 302 to maintain a driving engagement between chain 58 and drive gear 302. A chain tensioner (not shown) may be implemented to maintain proper driving engagement between drive sprocket 52, driven sprocket 60 and drive gear 302, if required.

A control gear 314 is axially moveable relative to and splined for rotation with intermediate shaft 304. An idler shaft 316 includes a first idler gear 318 and a second idler gear 320 fixed for rotation thereto. An output gear 324 is in constant meshed engagement with second idler gear 320. An actuation shaft 328 is threadingly coupled to a shift fork 330. Rotation of actuation shaft 328 translates shift fork 330. Actuation shaft 328 is supported for rotation in housing 305 and is fixed for rotation with output gear 324.

A control fork 332 is positioned within a groove 334 formed in control gear 314. An operator (not shown), similar to operator 174, may be used to axially translate control gear 314. Operation of range actuator 300 is substantially the same as previously described in relation to range actuator 20. It should be appreciated that the direct drive interconnection between actuation shaft 328 and shift fork 330 may be replaced with the carriage and spring arrangement previously described and vice versa. In addition, it should be appreciated that while actuators 20 and 300 have been depicted in conjunction with a multiple range sleeve shift system, the range actuators of the present disclosure may cooperate with any number of other shift systems including an axially moveable shift member.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A transfer case comprising: an input shaft; first and second output shafts selectively driven by the input shaft; a first gearset driven by the input shaft providing first and second gear ratios to the first output shaft; and a range actuator including: an axially moveable member operable to shift the first gearset between the first and second gear ratios; an actuation shaft drivingly coupled to the axially moveable member such that rotation of the actuation shaft translates the axially moveable member; a second gearset driven by the input shaft and driving the actuation shaft, the second gearset including a control gear moveable into and out of meshed engagement with a first gear as well as into and out of meshed engagement with an idler gear, wherein the actuation shaft is rotated in a first direction when the control gear is meshed with the first gear and rotated in a second opposite direction when meshed with the idler gear.
 2. The transfer case of claim 1, further including a power transfer mechanism drivingly interconnecting the first output shaft and the second output shaft, wherein the second gearset includes a drive gear fixed for rotation with a drive sprocket of the power transfer mechanism.
 3. The transfer case of claim 1, further including a power transfer mechanism drivingly interconnecting the first output shaft and the second output shaft, wherein the second gearset includes a drive gear in meshed engagement with a chain of the power transfer mechanism.
 4. The transfer case of claim 1, wherein the second gearset includes an idler shaft spaced apart from the actuation shaft, the idler gear and the first gear being fixed for rotation with the idler shaft, the second gearset also including a second gear fixed for rotation with the actuation shaft in meshed engagement with the first gear.
 5. The transfer case of claim 4, wherein the control gear is moveable to a position disengaged from each of the first gear and the idler gear.
 6. The transfer case of claim 5, wherein the control gear is fixed for rotation with and axially moveable relative to an intermediate shaft driven by the input shaft.
 7. The transfer case of claim 6, wherein the first gearset includes a planetary gearset circumscribing an axis about which the input shaft rotates.
 8. The transfer case of claim 1, further including a clutch drivingly interconnecting the input shaft and the second gearset.
 9. The transfer case of claim 1, further including an electric motor having an output shaft drivingly coupled to the control gear.
 10. The transfer case of claim 9, wherein rotation of the electric motor output shaft in a first rotary direction translates the control gear in a first linear direction and rotation of the electric motor output shaft in a second opposite direction translates the control gear in a second opposite linear direction.
 11. A transfer case comprising: an input shaft; first and second output shafts; a planetary gearset including a sun gear, a ring gear, a carrier and a pinion gear rotatably supported by the carrier, the pinion gear being meshingly engaged with the sun and ring gears; and a range actuator including first and second range sleeves being axially translatable between a first position to provide a drive connection between the input shaft and the first output shaft, a second position to provide a direct drive ratio connection between the input shaft and the first output shaft as well as the input shaft and the second output shaft, and a third position to provide a reduced speed drive ratio connection between the input shaft and the first output shaft as well as the input shaft and the second output shaft via the planetary gearset, the range actuator further including: an actuation shaft drivingly coupled to the first range sleeve such that rotation of the actuation shaft translates the first range sleeve; another gearset driven by the input shaft and driving the actuation shaft, the another gearset including a first gear, an idler gear and a control gear, the control gear being moveable into and out of meshed engagement with the first gear as well as into and out of meshed engagement with the idler gear, wherein the actuation shaft is rotated in a first direction when the control gear is meshed with the first gear and rotated in a second opposite direction when meshed with the idler gear.
 12. The transfer case of claim 11, further including a shift fork slidably positioned within a groove of the first range sleeve, wherein rotation of the actuation shaft translates the shift fork.
 13. The transfer case of claim 12, wherein the another gearset includes an idler shaft spaced apart from the actuation shaft, the idler gear and the first gear being fixed for rotation with the idler shaft, the another gearset also including a second gear fixed for rotation with the actuation shaft in meshed engagement with the first gear.
 14. The transfer case of claim 13, wherein the control gear is moveable to a position disengaged from each of the first gear and the idler gear.
 15. The transfer case of claim 14, wherein the control gear is fixed for rotation with and axially moveable relative to an intermediate shaft driven by the input shaft.
 16. The transfer case of claim 15, further including a clutch drivingly interconnecting the input shaft and the another gearset.
 17. The transfer case of claim 11, further including a power transfer mechanism drivingly interconnecting the first output shaft and the second output shaft, wherein the another gearset includes a drive gear fixed for rotation with a drive sprocket of the power transfer mechanism.
 18. The transfer case of claim 11, further including a power transfer mechanism drivingly interconnecting the first output shaft and the second output shaft, wherein the another gearset includes a drive gear in meshed engagement with a chain of the power transfer mechanism.
 19. The transfer case of claim 11, further including an electric motor having an output shaft drivingly coupled to the control gear.
 20. The transfer case of claim 19, wherein rotation of the electric motor output shaft in a first rotary direction translates the control gear in a first linear direction and rotation of the electric motor output shaft in a second opposite direction translates the control gear in a second opposite linear direction. 